7.3.4 Active Filter

The TLVx365 is an excellent choice for active filter applications requiring a wide bandwidth, fast slew rate,

low-noise, single-supply operational amplifier. Figure 7-6 shows a 500-kHz, second-order, low-pass filter using a

multiple-feedback (MFB) topology. The components have been selected to provide a maximally-flat Butterworth

response. Beyond the cutoff frequency, rolloff is −40 dB/dec. The Butterworth response is designed for

applications requiring predictable gain characteristics, such as the antialiasing filter used ahead of an ADC.

C

1

1 nF

C

2

150 pF

R

3

549 Ω

R

1

549 Ω

R

2

1.24 kΩ

V+

V

OUT

V

IN

V−

TLV365

Figure 7-6. Second-Order Butterworth, 500-kHz Low-Pass Filter

When considering the MFB filter, the output is inverted, relative to the input. If this inversion is not desired, then a

noninverting output can be achieved through one of these options:

• add an inverting amplifier

• add an additional second-order MFB stage

• use a noninverting filter topology, such as the Sallen-Key

Figure 7-7 shows the Sallen-Key topology.

V

OUT

V

IN = 1 VRMS

TLV365

R

3

150 kΩ

R

2

19.5 kΩ

C

3

220 pF

R

1

1.8 kΩ

C

1

3.3 nF

C

2

47 pF

Figure 7-7. Configured as a Three-Pole, 20-kHz, Sallen-Key Filter

7.4 Device Functional Modes

The TLVx365 have a single-mode of operation. The devices can be configured with unipolar supplies, split

and symmetrical bipolar supplies (±2.5 V, for example), or split and asymmetrical supplies (+4 V and –1 V, for

example). There are no power-down or low-power modes in the TLVx365.

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TLV365, TLV2365

SBOSAA8C – DECEMBER 2022 – REVISED AUGUST 2024

Copyright © 2024 Texas Instruments Incorporated

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